A look at a memorable moment in Seahawks history that occurred on March 31.

Gus Bradley isn’t just a glass-half-full kind of coach, the Seahawks’ defensive coordinator ordered a round of half-full glasses for the reporters this week when asked about his unit’s inconsistent efforts on third-down plays.

Think about it, the Seahawks have had games where they’ve been suffocating on the pivotal down – 1 of 12 against the 49ers, as well as New York Giants; and 3 of 14 against the Cardinals. But there also have been those games where they’ve helped breathe new life into the opposing offense on third downs – 9 of 16 against the Falcons; 8 of 15 against the Steelers; and 12 of 24 in last week’s loss to the Browns.

“It’s been every other game, so hopefully this week we’re better,” Bradley offered with a smile.

Using that theory – or oddity – the Seahawks are in line for one of their better efforts in Sunday’s game against the Cincinnati Bengals at CenturyLink Field. Because that is the consistently inconsistent pattern the third-down defense has followed this season: 49ers (good), Steelers (not so good); Cardinals (good), Falcons (not so good); Giants (good), Browns (not so good).

But why? How can a defense that has played so well on first and second downs have game-altering problems on third downs in some games and not others?

Like last week, when 44 percent of the Browns’ 298 yards came on those 12 third-down conversions. Like in the Week 2 shutout loss to the Steelers, when Ben Roethlisberger was 9 of 13 for 171 yards on third downs, compared to 13 of 17 for 127 yards on the Steelers’ other 53 plays.

It could be credited to playing tougher competition, because the Steelers are 5-2, the Falcons 4-3 and the Browns 3-3. But the 49ers are 5-1 and the Giants are 4-2 – and leading their divisions.

It could be credited to down-and-distance, as in giving up too many yards on first and second downs to allow the opposition to face more-makeable third-and-short situations. But the Browns converted on a third-and-14, a third-and-11 and on third-and-8 three times.

“We’re inconsistent on our third downs,” Bradley said.

Middle linebacker and leading tackler David Hawthorne says it’s a matter of executing properly.

“On most of the third downs last week, we were in great position,” Hawthorne said. “It was just a matter of making a play and getting off the field. It wasn’t like a busted coverage or a guy not knowing what he was doing. It was just a matter of seconds and not being there when the ball got there.”

Or getting there before the ball can be thrown. The Seahawks have 13 sacks, but “Leo” end Chris Clemons has almost half of them (five) and is the only player with more than one. The other D-linemen have combined for 2½ – one each by rush-end Raheem Brock and tackle Alan Branch, the half by end Red Bryant last week.

“On most of those plays, the quarterback made a play. He got away from us and made a play,” Brock said of the Browns’ Colt McCoy completing nine passes for 106 yards and also scrambling once for a first down on those 12 third-down conversions last week.

“There such a small margin for error on third downs. One step here or there, he gets away and makes a play.”

A big play on third down is more demoralizing than allowing one on first or second down because you were so close to getting off the field – especially when the conversion comes on third-and-long.

“It’s frustrating,” Brock said. “It frustrates you and then guys tend to get tired, which can lead to another big play. So it’s definitely frustrating.”

Another element has been the youth and physical style of the secondary. You play as aggressively as the Seahawks have, there are going to be the occasional open receivers.

The Seahawks will have their third starter at left cornerback this week, with rookie Richard Sherman taking over for Walter Thurmond – who started the past two games for Marcus Trufant. Thurmond (ankle) and Trufant (back) are now on injured reserve. There also will be a new nickel back – or old nickel back – with Roy Lewis coming off the physically unable to perform list for this game.

“We just have to focus and really concentrate on what they’re trying to do against us on third downs so we can get off the field,” Lewis said.

Like the Seahawks have done on first and second downs against the run. The Seahawks are allowing 3.2 yards per rushing attempt, which is tops in the league.

“You can run first- and second-down defense and have the big guys up front stop the run, but third downs is like a whole other world out there,” Lewis said. “Because it becomes a special down and it really depends on guys getting set up right, guys taking their preparation from the week into consideration, just coming on the field knowing exactly what they’re trying to do.”

Because one missed assignments or breakdowns is magnified on third down.

“Absolutely,” Lewis said. “Not getting off the field on third downs is no bueno. It’s no good.”